Method of carbureting air



Las.

Patented Aug. 270, 1929.

UNITED STATES PATENT OFFICE.

ROBERT OWEN KING, OF LONDON, ENGLAND.

METHOD OF CARBURETING AIR.

Application led September 7, 1926, Serial No. 133,911, and in Great Britain July 5, 1926.

This invention relates to an improved method of carbureting air more particularly for use in internal combustion engines. The invention has for its object the metering of air and liquid fuel in the most suitable proportions for a throttle-controlled internal combustion engine running under varying conditions of speed and load, by the use of a single air-metering restriction and a single fuel-metering orifice, both being of fixed d1- mensions, and without the use of any moving part other than the throttle.

The invention is hereafter described with reference to the annexed diagrammatic drawings in whichz- A Figure 1 is a sectional elevation with the throttle in the almost closed position.

Figure 2 is a plan of the top with the fiange attachment removed.

Figure 3 is a view similar to Figure 1 with the throttle and control valves in altered positions.

Figure 4 is a sectional elevation of part of Figure 1 showing the throttle in the fullest open position.

Figure 5 is a detail view in sect-ion and on a larger scale, of the fuel. orifice and adjacent parts.

A main air passageway A formed by a conical or upwardly convergent lower portion 1, a cylindrical or parallel central portion 2 and an outwardly coned or divergent vupper portion 3 has at its inner end 4 a flange 5 whereby the device may be bolted or otherwise attached to the4 induction pipe or manifold (not shown) of the internal combustion engine. shown provided with a cylindrical continuation 11 having therein a series of small holes 11. Shielding these holes 11 isa ring 10 having an inwardly turned flange 101, which ring is secured at its edge against an outer cylindrical casing 12. The ring 10 also bears against the end of the cylindrical continuation 11. This ring 1,0 forms an entrance throat to the main air passageway A and an air-metering inlet. The cylindrical portion 2 forming a second throat is provided with a throttle device, this throttle being of any suitable type but shown as a sliding plate 6 movable in a. housing 7 formed with or secured to the outer casing 12. This throttle plate 6 is shown with an operating handle 8, which may be of any convenient construction, and can beactuated to slide transversely across the second throat 2 so as to vary The conical portion 1 is the cross sectional area of the opening available. The plate 6 is shown guided in slots 13 in the casing 12, and its leading edge 61 may be straight or, if preferred, curved to the same radius as the interior of the throat 2. In Figure 2 the plate 6 is shown curved at front.

The second throat 2 is of smaller cross sectional area than the entrance throat formed by ring 10 so that as air passes up the passageway, its velocity is increased.

The casing 12 is shown provided with a float feed chamber 14 having a fuel supply orifice 15 and a conventional float 16 and needle valve 17. The supply of liquid fuel to the chamber 14 may, however, be effected andcontrolled in any suitable manner. The fuel supply orifice 15 consists of a hole in the cover 18 of a well 19. 'This well is formed by walls 20, 201 integral with the casing 12. The Well is in communication with a chamber 21 formed inside the casing 12 and outside the convergent wall 1 and its cylindrical continuation 11, and through the holes 11, with the space between the flange 101 of the ring 10 and the cylindrical continuation 11. Between said Well 19 and the chamber 21 is a controlling device represented as a butterfly valve 22 having a setting lever 27, whereby such communication can be adjustably restricted or regulated. By way of example, the means of restriction is shown as a butterfly valve. Alternatively the necessary amount of restriction may be provided by suitably fixing the total area of the pressure-communicating holes 11.

Depending into the well 19 and arranged immediately above the fuel supply orifice 15 is one end 23 of a branch passageway 24 which extends to the second throat 2 in such a manner that fuel lifted into said branch passageway 24, as hereafter described, can be translated along said passageway and delivered at outlet 25 into said throat 2. The outlet 25 is on the side of the throat 2 remote from the housing 7 so that the leading edge of throttle plate 6 is moved towards said outlet 25 as the throttle closes the bore of throat 2.

Below the throttle plate 6 is a slot 26 communicating with the passageway 261 which leads to the chamber 21. When the plate 6 is in the nearly closed position, the opening of the slot 26 into the throat 2 is shielded from the velocity of the air passing the leading edge 61 of the plate 6. As

the plate 6 is withdrawn into its casing however, the opening of the slot 26 becomes increasingly exposed to the velocity of the air passing the said edge of the plate-6. Vxhen the plate is fully withdrawn into its casing, the upper end of the passageway 261 is fully exposed to the effect of the air velocity in the throat 2, as shown in Figure 4.

The carburetor represented on the annexed drawings is formed in upper and lower halves separated by a bakelite gasket or the like 28, the halves being secured together by screws 29, 30.

In operation, the air drawn in by the suction of the engine (i. e. the depression in the manifold) passes through the entrance throat 10, the main passageway A and the smaller' throat 2. By means of this air streamra static depression is caused in the chamber 21, which chamber is vseparated from the throat 10 and is in communication with the main passageway A by means of 'the holes 11 which are so placed as not to be exposed to the direct velocity of the air passing through the throat 10. The chamber 21 being in communication with the well 19, the said static depression acts on the fuel orifice 15 in such a manner as to cause fuel to well up or issue from the chamber 14 through the said orifice 15, and the shape of the fuel orifice is such as to eliminate largely the effects ofifuel viscosity; the weight of fuel so issuing from the orifice 15 will bear a nearly constant proportion to the weight of air passing through the entrance throat 10, except as modified by arrangements de scribed hereinafter.

The air drawn in by the suction of the engine has its velocity increased after passing the entrance throat 10, by passing through the smaller throat 2, so the depression in this throat is always greater than the depression communicated from the entrance throat 10 to the well 19. This increased depression is communicated to the well 19 and to the fuel orifice 15 by means of the branch passageway 24, and increases the depression already existing in the well. The depression in the branch passageway is further increased, at less thanopen throttle positions, by placing the end 25 which opens into the smaller throat 2 so that it is acted on by the velocity of the air passing the leading edge 61 of the throttle plate 6, so that the depression in this passageway24 is proportional to the depression in the induction manifold,

Ithat is the engine side of the throttle. This increased depression communicated to the well 19 and to the fuel orifice 15 by the passageway 24, insures that a flow of air always exists from the well through the branch passageway into the smaller throat 2 and this flow of lair carries with it any fuel that wells or risesl up from the orifice 15, the mouth 23 'of 'the branch passageway being the main air passageway A, and consequently the extent of the said increase of depression can be determined by fixing the relation of the area of cross section of the relieving passageway 20-21-11 to the area of cross section of the branch passageway 24, and thereafter the said increase of depression can be further increased by restricting the area of cross section of the relieving passageway 20-211l by such means as ythe valve 22 in the passageway between the wall 201 and the exterior of the throat 2.

The area of cross section of the branch passageway 24 is generally somewhat larger than the area of cross section of the fuel orifice and the two parts are separated by a suflicient distance (say two to three times lthe bore of the mouth 23) so that the depression on the fuel orifice is not materially increased by the proximity of the mouth 23 of the branch passageway 24 into which a small amount of air is drawn at high speed, more particularly at nearly closed throttle positions, when the delivery end 25 of the branch passageway is exposed substantially to the very high depression then existing normally in the induction system and at the throttle edge 61. The arrangement of the branch passageway 24 as described, provides for an increase of fuel flow as the throttle is closed, over that due to the depression from the entrance 10, since as the throttle is closed, the Adepression on the delivery end 25 of the branch passageway 24 is increased and this increases the rate of the flow of air through the branch passageway 24 and the depression in the well 19 and on the fuel orifice 15.

The action of the manifold depression and of the velocity depression during the almost closed and partly closed portions -of the throttle, is shielded from the slot 26 by reason of the plate 6 above said slot projecting into the bore of the second throat 2; when, however, the throttle plate is retracted to open the throttle and until its leading edge is flush with the wall of the throat the slot 26 is exposed to an increasing extent to the Ve` locity depression in the smaller throat 2. This depression is communicated by the slot 26 via the passageway 261 to the chamber y21 and thence to the fuelorifice 15, producing 'an increase of fuel flow as the throttle 6is '20 and holes 11 to the higher pressure in moved to its fully open position, the increase depending on the extent to which the extra depression is relieved by the holes 11 opening to a higher pressure, this in turn depending on the relative areas of cross section of the holes ll and of the slot 26. In order to provide for a further increase of fuel flow at fully open throttle, the plate 6 may, by being retracted further into its case, increase the area communicating the depression in the throat 2 to the chamber 21 thus further increasing the depression in this chamber and on the fuel orifice 15. As before, the magnitude of the increase will depend on the extent to which it is relieved by the holes l1 opening to a higher pressure.

The extent of the total enrichment obtained by this method depends on the relation of the total area of the radial holes 1l opening into the annular space around flange 101l at the foot of the main air passage space, to the area of the passageway 26 leading from the annular chamber 21, and the relative areas of the two throats or air restrictions 10 and 2 respectively, and also on the distance apart of the two restrictions l() and 2, since there is a recovery of pressure between them depending on their distance apart. All of these proportions can be fixed for any particular case.

The improved method of carbureting described has the further advantage that the metering of air and fuel is not affected to any appreciable extent by air vibration in the induction system; thus the setting with respect to the sizes of the fuel orifice 15 and air metering orifice l0 is not affected, as is usually the case, by the characteristics of the induction system and by engine valve timing. The reason for this is that air vibrations take effect mainly in the second throat or central restricted portion 2 of the main air passage and especially at the more open throttle positions. These vibrat-ions affect the suction on the branch passage 24, but at the more open throttle positions the suction on this passageway 24 has a negligible effect on the flow of fuel through the orifice l5; hence this flow of fuel is not affected by the air vibrations in the main passage A-A. Air vibrations may extend to the first throat or air metering restriction 10, but their action on this part differs from that on the branch passage 24, because the velocity head of air vibrating or passing out in the reverse direction is converted mainly into pressure head at the lower throat 10, so that instead of causing a suction atthe radial openings 11 leading to the fuel jet, this velocity produces a pressure and tends to stop the flow of fuel. That is, only air entering in the normal direction induces a flow of fuel from the jet, while air passing out tends to stop the flow of fuel; correct metering is thus maintained, irrespective of air vibrations.

Having thus described my invention what arranged outside said main passageway,

apertures in said passageway allowing communication between said air column and said static depression chamber, means for controlling the degree of static depression independently of the rate of flow of the air column, means for supplying liquid fuel to a fuel orifice located outside said main passageway, a branch passageway extending from above said fuel orifice into the contracted throat of said main passageway, a device for adjustably choking said air column in the constricted throat portion of said main passageway, and a communication channel between said contracted throat portion and said static depression chamber, said channel being normally shielded by the said adjustable choking device.

2. A carburetor, comprising a main pas-v sageway for a moving column of air, an airmetering inlet ring and a contracted throat to said passageway, a chamber arranged outside said main passageway, means for forming a static depression in said chamber by means of the moving column of air, a fuel orifice also arranged outside said passageway, and means for supplying liquid fuel to said fuel orifice, said fuel orificebeing subjected in a variable degree to said static depression, a branch passageway extending from the contracted throat of the main passageway to above said fuel orifice so that fuel lifted into said branch passageway will be delivered into said contracted throat of the main passageway, a sliding withdrawable throttle plate adapted to be projected into said contracted throat, a permanently open communication channel between said contracted throat and said static depression chamber, said channel being in the throat opposite to the delivery end of the branch passageway and immediately in front of the said throttle plate and an extension of said channel which is normally covered by said withdrawable throttle plate but is exposed when said throttle plate is further withdrawn.

3. A carburetor comprising a main air conduit having a flared entrance and a restricted portion, a casing embracing and spaced .from the conduit, said conduit at the flared portion being provided with openings placing the space between the casing and conduit in communication with the conduit, a fuel well in communication with the space, a valve for controlling communication between the space and well and a restricted conduit connecting the well with the restricted portion of the air conduit.

4. A carburetor, comprising a main passageway for a moving column of air, an airlnetering inlet-ring to said passageway, a contracted throat to said passageway7 said contracted throat being of smaller area than said inlet ring, a static depression chamber arranged outside and around said main passageway, a series oi apertures in said passageway allowing communication between said air column and said static `depression chamber, means for controlling the degree of static depression independently of the rate of flow of the air column, means for supplying liquid fuel to a fuel orifice located outside said main passageway, a branch passageway extending from above said fuel orice and into the contracted throat of said Inain passageway and an adjustable device for choking said moving air column in said contracted throat portion of the main passageway.

In testimony whereof I hereunto aix my signature.

ROBERT OWEN KING. 

